A Tunisian boat carrying around 40 African migrants has been stranded off the country's coast without aid for more than a week after authorities refused to let them disembark there, the Red Crescent said on Monday.

Monji Slim, an official of the Tunisian Red Crescent, said the authorities had argued that Malta or Italy should accept the migrants. The Tunisian interior ministry declined to comment.

Slim told Reuters the boat was stuck 12 miles off the coast. "The African migrants at sea are in a bad condition after the vessel's captain refused to receive aid to pressure the Tunisian authorities to receive them, but no solution has been reached after 11 days at sea."

Last week, NGO WatchTheMed, which runs migrant sea rescue hotline Alarm Phone, indirectly accused Malta of breaking international law when it escorted the vessel into Tunisian waters. 

The government vehemently denied that allegation, saying that it had directed the vessel to the closest safe port, as it was obliged to do by law. 

It was not clear from where the migrants had originally set off before they were rescued by the Tunisian vessel.

The new Italian government has closed its ports to charity ships operating in the Mediterranean, saying the European Union must share the burden of accepting the hundreds of migrants who are plucked from waters each month, mostly off the Libyan coast.

Rome called this month for migrant centres to be set up in Africa to stop a tide of asylum-seekers fleeing toward western Europe. Tunisia has rejected this proposal.

At least 80 migrants died when their boat sank off the Tunisian coast last month, one of the worst migrant boat accidents in the North African country of recent years.

Human traffickers are increasingly using Tunisia as a launch pad for migrants heading to Europe as the Libyan coast guard, aided by armed groups, has tightened controls.